Use of dibutyl malate as insect attractant

ABSTRACT

The invention relates to the use of dibutyl malate as an attractant for domestically occurring flies, particularly of the species Musca domestica and Fannia canicularis, and to insect traps characterized by emanating dibutyl malate vapors. Preferably the dibutyl malate is diluted before evaporation with a liquid diluent or a solid diluent or carrier such that the concentration in or on the trap is below 10% by weight.

This application is the national phase of international applicationPCT/EP95/02614 filed Jul. 5, 1995 published as WO96/01052 Jan. 18, 1996,which designated the U.S.

The present invention relates to the use of dibutyl malate as anattractant for certain insects and to insect attracting devices intendedfor trapping or killing flies comprising dibutyl malate as anattractant. Particularly, the invention concerns the use of dibutylmalate for attracting domestically occuring flies such as the housefly(Musca domestica) and the lesser housefly (Fannia canicularis).Furthermore the invention concerns a method for catching flies usingdibutyl malate as an attractant.

Although most domestically occuring flies, like the common house fly, donot present a direct nuisance or health hazard to the human body, as dobiting or stinging insects, they do present a hygiene problem in thatthey may infect food with pathogenic microorganisms and thus acceleratefood spoilage. Therefore there is a need for combatting flies inenvironments where food is stored or prepared. Moreover, many peopleconsider flies a nuisance in their homes. Compounds which are able toattract flies can play an import role in combatting them by luring theminto traps where they are killed or immobilized.

Various compounds and compositions attracting house flies, oftentogether with other insects, have been described in U.S. Pat. Nos.4,764,367, 4,801,446, 4,801,448, 4,808,403, 4,859,463, 4,880,625,4,911,906, 4,959,209, 4,988,507 and 4,988,508. One of the compoundsmentioned is dibutyl succinate, but this appears to be an attractant forother insects than Musca domestica.

The insect attractant properties of a large number of compounds for tendifferent insect species have been compiled by M. Beroza and N. Greenand described in Agriculture Handbook No. 239, published in 1963 by theAgricultural Research Service of The USA Department of Agriculture.Several esters of malic acid were reported to be slightly attractive tovarious fruit flies, Gypsy moth and Drosophila; no data for the housefly were reported.

On the other hand dibutyl malate and various other malate esters werereported as effective repellents against:

various biting insects, U.S. Pat. No. 4,047,505;

biting midges, Mosq. News, 43(3) 1983, 338-342;

yellow fever mosquitoes, J. Econ. Entomol. 60(6) 1967, 1587-1590;

black flies, J. Econ. Entomol. 44 1951, 813-814;

sand flies, Proc. New Jersey Mosquito Exterm. Assoc. 37 1950, 154-156;

tsetse fly, Trans. Royal Soc. Trop. Med. Hyg. 40(3) 1946, 341-344.

Furthermore, dibutyl malate was reported as an effective insectrepellent in J. Am. Chem. Soc. 71 1949, 507-509.

Finally malic acid (but not any malate ester) is mentioned as acomponent of an insect attractant composition in Japanese Patent ApplnNo. 54.095732.

It has now been found that dibutyl malate is a powerful attractant fordomestically occuring flies, more particularly the housefly (Muscadomestica) and the lesser housefly (Fannia canicularis), and thus can beused in a method for catching flies by luring them into or onto aninsect attracting device or insect trap. The compound can be used forthis purpose, either as such or in combination with other insectattracting substances. Therefore, insect attracting devices or trapsaccording to the invention are characterized by emanating dibutyl malatevapors, thus causing a concentration gradient of dibutyl malate in theatmosphere surrounding them which will lure the flies into or onto thetrap. Conventionally such traps also comprise means for killing orimmobilizing the flies e.g. a toxic substance with which the fly isbrought into contact, a tacky surface from which the fly cannot escapeonce it has landed thereon, some electric killing device or any otherkilling or immobilizing means known in the art. Furthermore trapsintended for domestically occuring flies are generally specificallydesigned for trapping flying insects, e.g. by providing a means forhanging them from a ceiling, and are generally used indoors.

Dibutyl malate is a liquid at room temperature. It is substantiallyinsoluble in water but soluble in isopropanol, diethyl ether, hexane andother low polar or non-polar organic solvents.

Preferably the dibutyl malate is diluted, either after evaporation fromthe trap by adding a gaseous diluent such as air, or before evaporationfrom the trap by mixing with a liquid or solid diluent. In the lattercase the concentration of dibutyl malate in or on the trap is preferablybelow 10% by weight, more preferably between 5 and 0.0001%. The optimumconcentration for a specific kind of application depends on the diluentused and the construction of the trap and can be determined by simpleexperimentation with a range of concentrations.

A suitable liquid diluent may be water, in which dibutyl malate may bedispersed using some conventional dispersing means such as anemulsifier, or it may be an organic liquid such as those mentioned aboveor mineral oil, polyethylene glycol, vegetable oil, parrafin, a resinousmaterial or the like. Solid diluents or carriers may be wood, paper,textile, porous organic polymers or inorganic absorbent media such aszeolites, silica, activated carbon, aluminium oxide and the like fromwhich dibutyl malate can evaporate at a desired rate.

The fly-attracting properties of dibutyl malate are illustrated in theexamples below:

EXAMPLE 1

The attracting properties of dibutyl malate were tested using theolfactometer made of transparent perspex as depicted in FIG. 1. Theexposure chamber has the shape of a four-pointed star, with an inlettube at each point of the star. Gases are sucked into the exposurechamber through the inlet tubes and drawn out by a pump connected to anopening in the centre of its floor. The shape of the exposure chamberwith its curved walls prevents the four air flows from mingling andcreates sharp borderlines between the adjacent fields (indicated in FIG.1 by A, B, C and D). The olfactometer was placed in a room kept at22°±2° C. and constant relative humidity. No daylight could enter theroom and it was lit by fluorescent tubes. The flies used in this testwere of the species Fannia canicularis.

A test tube containing a solution of dibutyl malate in ethanol wasattached to inlet tube A such that the air sucked in via this tubecarried the dibutyl malate vapors with it. Identical test tubes withpure ethanol were attached to the other inlet tubes. A fly was placed atthe centre of the exposure chamber and allowed to acclimate for 5minutes whereafter the air flows were sucked into the chamber. Theposition of the fly was recorded at 30 second intervals for 10 minutes.The percentage of time that the fly spent in sector A was calculated.The experiment was repeated with different concentrations of dibutylmalate and for each concentration with 10 flies. The results arepresented as a bar graph in FIG. 2, which clearly shows that dibutylmalate clearly acts as a fly-attractant at concentrations between 1 and0.0005% in ethanol.

EXAMPLE 2

This experiment was carried out in the same room as used in Example 1.

A volume of 2 ml of a solution of dibutyl malate in 70% aqueous ethanolwas mixed with enough Aerosil 200* to form a paste. This paste wasapplied to the top of a 25 cm×10 cm sheet of yellow card. This colouredcard was chosen because in other tests this particular shade of yellowproved to be attractive to Fannia canicularis. The yellow cards werepreviously coated with a clear odourless glue. The yellow baited targetcard was hung at one end of a tank (120 cm×38 cm ×30 cm) and the tanksealed. 20 flies of the species Fannia canicularis were released at theother end of the tank and thereafter the tank remained sealed for 18hours, after which the number of flies stuck to the card was recorded.

The test was repeated with four different concentrations of dibutylmalate and with pure 70% aqueous ethanol as a control. The results arepresented as a bar graph in FIG. 3, from which it can be seen that inthis experiment dibutyl malate at a concentration of 0.1% luredsignificantly more flies to the target than the control, and that theattractancy is concentration dependent.

EXAMPLE 3

In this experiment the same room was used as in Examples 1 and 2 and thesame yellow cards prepared in the same way as in Example 2. The fliesused were of the species Musca domestica and Fannia canicularis.

A baited target card was hung from the ceiling of the room for each testwhile at the same time a control card, also treated as the control cardin Example 2, was hung from the ceiling. An undetermined number of flieswere released in the room. The room was kept closed for 4 hours,whereafter the number of flies on the baited card and the control cardwas counted. The results are presented in FIG. 4.

We claim:
 1. An insect trap for domestically ocurring flies comprisingmeans for emanating dibutyl malate vapors to the surrounding atmosphereand means for killing or immobilizing the flies.
 2. An insect trapaccording to claim 1 wherein the fly killing or immobilizing meanscomprises a toxic substance, a sticky substance or an electric killingdevice.
 3. A method for catching domestically occurring flies whichcomprises exposing said flies to dibutyl malate vapors emanating from aninsect trap thereby causing a concentration gradient of dibutyl malatein the atmosphere surrounding the flies which will lure the flies intoor onto the trap.
 4. A method according to claim 3 wherein the fliesbelong to the species Musca domestica and Fannia canicularis.
 5. Amethod according to claim 3 or 4 wherein the dibutyl malate is dilutedwith a gaseous, liquid or solid diluent.
 6. A method according to claim5 wherein the dibutyl malate is diluted before evaporation with a liquiddiluent or a solid diluent or carrier.
 7. A method according to claim 6wherein the concentration of dibutyl malate in or on the trap is below10% by weight.
 8. A method according to claim 7 wherein theconcentration of dibutyl malate is between 5 and 0.0001% by weight.